A seat fixing device for fixing a seat to a floor of an airplane is already known, the seat fixing device having horizontal fixing means and vertical fixing means. During installation, first of all the vertical fixing means are introduced into recesses of a fixing rail. Subsequently, the seat fixing device is displaced in the longitudinal direction of the fixing rail, so that the vertical fixing means come to lie under side flanks of the fixing rail and the horizontal fixing means can be introduced positively into the recesses of the fixing rail in the longitudinal direction of the fixing rail. Subsequently, by means of an actuating unit of the seat fixing device, which actuating unit is designed as a locking unit, the horizontal fixing means are positively locked in their vertical direction and the vertical fixing means are non-positively clamped under the side flanks of the fixing rail.